The Collaborative International Dictionary of English v.0.48:

Unmanned \Un*manned"\, a.
   1. [Properly p. p. of unman.] Deprived of manly qualities;
      deficient in vigor, strength, courage, etc.; weak;
      effeminate.
      [1913 Webster]

   2. [Pref. un- not + man + -ed.] (Falconry) Not tamed; not
      made familiar with, or subject to, man; -- also used
      figuratively. [Obs.]
      [1913 Webster]

            Hood my unmanned blood bating in my cheeks
            With thy black mantle.                --Shak.
      [1913 Webster]

   3. [Pref. un- not + manned.] Not furnished with men; as, an
      unmanned ship.
      [1913 Webster]

WordNet (r) 3.0 (2006):

unmanned
    adj 1: lacking a crew; "an unmanned satellite to Mars" [syn:
           unmanned, remote-controlled] [ant: manned]